It is proposed to do direct electro-physiological studies of synapses made by hippocampal neurons in culture, focusing on synaptic mechanisms involved in epilepsy. This work draws on two experimental advances of our group. One is a technique I have developed for growing "microcultures" of central nervous system neurons. These microcultures can contain as few as one neuron, and can survive for as long as several months. The other advance is an in-vitro epilepsy model of Furshpan and Potter (1988) that involves dissociated hippocampal neurons that are grown for prolonged periods in culture in the presence of blockers of synaptic activity (such as kynurenic acid and magnesium). When the cultures are returned to regular growth medium, the neurons produce intense bursts of electrical activity that closely resemble the seizure activity recorded from the intact hippocampus. Aims for the project are: - To study synapses in hippocampal microcultures. Microcultures are a useful general method for physiological and pharmacological studies of synaptic interactions, with some significant advantages over other experimental models such as cortical slices. Neurons and their circuitry will be categorized by collecting information about spontaneous firing patterns, synaptic inputs and synaptic outputs, and iontophoretic responses. - To simplify the model of epileptiform activity in mass-cultures of thousands of neurons down to smaller numbers of neurons in minicultures and microcultures, in order to study the phenomenon of epilepsy at the level of individual synapses in a system consisting of only several neurons. The abnormalities of the chronically blocked cultures will be investigated to determine the cause of the epileptiform activity in this model system. The model system will be used to investigate pharmacological treatments of epilepsy that are targeted at specific subgroups of neurons, to avoid current epilepsy treatments.